The present invention relates to methods of making pyrrolidones, especially N-methyl pyrrolidone (xe2x80x9cNMPxe2x80x9d), by hydrogenation.
Olsen, in U.S. Pat. No. 4,841,069 described reactions of succinic anhydride, methanol and hydrogen. In Example 1, Olsen described a reaction in which 67 g of succinic anhydride, 62 g of methanol, and 12.53 g of ammonia were heated 5 hrs in an autoclave at 300xc2x0 C. with stirring. Olsen reported that 100% of the succinic anhydride was converted with a selectivity to N-methylsuccinimide (xe2x80x9cNMSxe2x80x9d) of 90%. In Example 11, Olsen described a reaction in which 65 g of succinic anhydride, 41 g of methanol, and 12.15 g of ammonia, 12 g of 5% palladium on carbon catalyst, and 700 psig of hydrogen were heated 21 hrs at 290xc2x0 C. with stirring. Olsen reported that 100% of the succinic anhydride was converted with a 60% selectivity to N-methylsuccinimide and a 30% selectivity to N-methylpyrrolidone.
Olsen, in U.S. Pat. No. 4,814,464 (which is very similar to U.S. Pat. No. 4,841,069), described the same or similar ammonolysis-alkylation reactions in which a succinic derivative such as the anhydride, acid or diester is reacted with ammonia and a C1 to C4 alkanol and converted to an N-alkylsuccinimide. Olsen stated that xe2x80x9cIn general, the reactants, substrate, ammonia, and alkanol, are used in about stiochiometric proportions. Too little ammonia or alkanol results in incomplete conversion, and too much ammonia is wasteful and produces undesirable by-products.xe2x80x9d However, Olsen also states that xe2x80x9cpreferably excess of the alcohol is used.xe2x80x9d It is reported that products can be separated by distillation or crystallization. See Col. 3, lines 50-59.
Olsen also remarked that the N-alkylsuccinimide can be reduced catalytically with hydrogen either continuously or batchwise. In Example 1, Olsen reported hydrogenating NMS at 230 C. for 2 hours over a nickel catalyst to yield a 60% NMS conversion with an 89% selectivity to NMP. In Example 3, Olsen reported reacting 73g dimethylsuccinate, 37 g ammonium hydroxide, 12 g of 5% palladium on carbon catalyst, and 700 psig of hydrogen for 21 hrs at 290 C. with stirring. Olsen reported that 100% of the dimethylsuccinate was converted with a 70% selectivity to N-methylsuccinimide and a 20% selectivity to N-methylpyrrolidone.
Koehler et al., in U.S. Pat. No. 5,101,045, described a process for the preparation of N-substituted pyrrolidones by catalytic hydrogenation of maleic anhydride, maleic acid and/or fumaric acid in the presence of ammonia, a primary alcohol and a modified cobalt oxide catalyst. In Example 3, Koehler et al. stated that 75 ml of a 45% aqueous diammonium maleate solution and 75 ml methanol were hydrogenated for 42 hours at 230 C. in the presence of 10 g of a modified cobalt oxide catalyst. Koehler et al. reported that the product contained 89 mol % NMP, 5.0 mol % pyrrolidine and methylpyrrolidine, and 2.7 mol % of succinimide and methylsuccinimide.
Liao, in U.S. Pat. No. 3,092,638, and Hollstein et al., in U.S. Pat. No. 3,681,387, described hydrogenating succinimide. Hollstein et al. run the hydrogenation in water over a palladium on carbon catalyst.
Liao, in U.S. Pat. No. 3,080,377, Himmele et al., in U.S. Pat. No. 3,198,808, Hollstein et al., in U.S. Pat. No. 3,681,387, and Pesa et al. in U.S. Pat. No. 4,263,175 described hydrogenating succinic acid or succinic anhydride in the presence of ammonia to yield 2-pyrrolidone. Catalysts used include: palladium on carbon, ruthenium on carbon, ruthenium on alumina, and cobalt oxide. Himmele et al. stated that an ammonium salt can be used in place of ammonia.
Chichery et al., in U.S. Pat. No. 3,448,118, and Weyer et al. in U.S. Pat. Nos. 5,157,127 and 5,434,273, disclosed methods of making N-substituted pyrrolidones in which succinic anhydride, succinic acid, or the like is hydrogenated in the presence of a primary amine. Chichery et al. run their hydrogenations in water with a palladium on charcoal catalyst. Weyer et al. used a modified cobalt oxide catalyst.
zur Hausen et al., in U.S. Pat. No. 4,780,547, described hydrogenation of NMS over a nickel catalyst. In Example 2, zur Hausen et al. stated that comparable results can be obtained using succinic anhydride and methylamine in place of NMS.
The invention provides methods of making a compound having the formula: 
wherein R1, R2, R4, and R5 are, independently, H or a C1 to C6 alkyl or substituted alkyl; and R3 is H or a C1 to C6 alkyl or substituted alkyl. These methods involve hydrogenation.
In a first aspect, a composition containing a compound having the formula: 
wherein R1, R2, R4, and R5 are, independently, H or a C1 to C6 alkyl or substituted alkyl; or wherein R2 and R4 together are replaced by a double bond; R3 is H or a C1 to C6 alkyl or substituted alkyl; and X and Y are, independently, OH, Oxe2x88x92, or where X and Y together are a bridging oxo; is reacted with hydrogen, in the presence of water and a catalyst. Preferably, the catalyst includes carbon, metal oxide and at least one metal selected from Pd, Rh, Pt, Ru, Ni or Co. In some embodiments, a compound of formula (A) is purified prior to hydrogenation. Thus, in some embodiments, a compound of formula (C) is made in a process having at least 3 steps. In a first step, a compound of formula (B) is reacted with an ammonia source, in the presence of water, to form a compound having formula (A). Then, in a second step, the compound of formula (A) is extracted into an organic solvent. In a third step, the compound of formula (A), that was extracted in the second step, is hydrogenated in the presence of a catalyst.
It has also been surprisingly discovered that, in some processes, the yields of compound (C) can be increased substantially by hydrolyzing compositions formed during hydrogenation reactions of compounds (A) and/or (B). A portion of the composition formed by hydrogenating (A) and/or (B) can be hydrolyzed (i.e., reacted with water) to produce a compound or compounds of formula (C); this portion is referred to as a compound (C) precursor. To prevent over-reduction (and lower yields), the compound (C) precursor is separated from hydrogen, the hydrogenation catalyst, or both hydrogen and the catalyst.
In another aspect, the invention provides a method of making a compound of formula (C), in which a composition including a compound having the formula: 
wherein R1, R2, R4, and R5 are, independently, H or a C1 to C6 alkyl or substituted alkyl; and R3 is H or a C1 to C6 alkyl or substituted alkyl; is reacted with and hydrogen in the presence of a Pd, Rh, Pt, Ru, Ni or Co catalyst; at a temperature of less than 220xc2x0 C. and for a time of less than 10 hours. In this method, compound (C) is obtained in a yield of at least 80%.
Advantages of various embodiments of the present invention include: higher yields, better purity, more stable catalysts, lower reaction temperatures, shorter reaction times, and lower costs. Unexpectedly superior results were discovered under various conditions, including: using a metal oxide (such as zirconia) textured catalyst; hydrogenating a succinimide below 220xc2x0 C. for less than ten hours; and hydrogenating aqueous phase compositions having a relatively high concentration of compound (B).
For fermentation or other biologically-derived compositions, it is desirable to separate out proteins and other contaminants, prior to the hydrogenation to produce compound (C). For example, proteins in these compositions could poison a hydrogenation catalyst. Thus, there may be important advantages in separating out an imide, such as compound A, and hydrogenating the extracted imide. An extraction step prior to the formation of N-methylpyrrolidine can produce unexpectedly superior results, especially for biologically-derived starting materials.